1. Field of the Invention
The present invention relates to a binocular loupe which is used during medical surgery or precision machine operation, and in particular, relates to a method for manufacturing a binocular loupe in which loupe units are attached to carrier lenses in a frame.
2. Description of Related Arts
Conventionally, binocular loupes have been widely used as means to stare a target locally at hand in an enlarged manner in a variety of fields such as medical fields, precision machining, jewel processing, and the like. In such fields, it is required to be capable of staring with a high degree of accuracy.
As illustrated in FIG. 1, a binocular loupe 10 being a general lens fitting type is configured to include a frame 1 having the same structure as glasses to correct eyesight of an operator, loupe units 2 being a binocular loupe main body for enlarging an image of an operational target, carrier lenses 5 to which the loupe units 2 are attached as being fitted to the frame 1, attaching portions 3 for attaching the loupe units 2 to the carrier lenses 5, and frame temples 6 to be worn on the face of the operator. The loupe units 2 are inserted to opening portions which are formed at the carrier lenses 5 by performing cutting at the surface and is fixed with the attaching portions 3.
FIG. 2 is an explanatory view illustrating a state that the operator wears the binocular loupe 10. Similarly to normal grasses, the binocular loupe 10 can be worn to the face section with the frame temple portions 6 of the frame 1 hooked on the ears of the operator.
When the binocular loupe 10 having the above configuration is used especially in a medical field, the binocular loupe 10 is required to be matched to an inter-pupil distance and a working posture of each operator as being fatal to humans. In order to ensure a high degree of visibility, manufacturing is performed according to the following procedure in accordance with physicality of the operator.
(1) Selecting Frame Fitted to Physicality of Operator's Face
Here, the frame temple portions 6 fit to temporal regions of the head of the operator and curved leading end portions of the frame temple portions 6 appropriately hang on the ears. A nose pad which is arranged between a pair of the carrier lenses 5 is perfectly contacted to the glabella of the operator.
(2) Measuring Inter-Pupil Distance with PD Meter
In general, an inter-pupil distance is measured using a PD meter (for example, see Patent Literature 1). A viewing port for a measurer is arranged at one end of the PD meter and a window through which a subject sees the inside of a body is arranged at the other end thereof. The subject brings his/her eyes close to the window to stare a mark appearing in the body. When the measurer causes the right and left pupils of the subject to be matched by performing necessary operation during viewing through the viewing port, the PD meter optically reads out the image at that time. Then, the PD meter measures the inter-pupil distance and distances from the nose center to the centers of the right and left pupils of the subject and displays the result. At that time, the PD meter performs the measurement based on a previously-determined focal distance being 40 cm, for example. FIG. 3 illustrates an example of a measurement result performed with the PD meter. In FIG. 3, a numeral value at the left side denotes a distance from the nose center to the pupil center of the right eye of the subject, a numeral value at the right side denotes a distance from the nose center to the pupil center of the left eye of the subject, and a numeral value at the center denotes a distance between pupils of both eyes.
Meanwhile, a posture when an operator (a doctor) performs operation (a posture during surgery) looks as illustrated in FIG. 4 as the operator being in a state of staring a leading end of holding equipment (an operational manipulating position P). Although loupe units 2 are eliminated from a frame worn by the operator in FIG. 4, the operator observes the operational manipulating position P through loupe units 2 in an enlarged manner. Accordingly, for attaching the loupe units 2 to the frame 1, the loupe units 2 are not supposed to be attached as being perpendicular to a surface of the carrier lenses 5 of the frame 1. Here, it is required that the loupe units 2 are inclined downward (toward a lower frame edge side) as illustrated in FIG. 2 in the vertical direction and are inclined inward (toward a nose pad side) as illustrated in FIG. 5 in the horizontal direction.
Angles at which the right and left loupe units 2 are inclined inward are derived from the measurement result of the inter-pupil distance with the PD meter. According to the measurement result of FIG. 3, the distance from the center line L at the nose center to the center of the pupil of the right eye is 31 mm and the distance therefrom to the center of the pupil of the left eye is 29.5. Further, the measurement was performed with the focal distance set to 40 cm. Thus, inward wearing angles p, q being inward attaching angles of the right and left loupe units 2 to be attached to the surfaces of the right and left carrier lenses 5 are detected, respectively.
(3) Measuring Distance from Eyes to Operational Manipulating Position
The operator wearing the frame 1 without the loupe units 2 attached takes a working posture as illustrated in FIG. 4. In this state, a distance from eyes to the operational manipulating position P is measured by measuring a distance from the operational manipulating position P to a connecting part of the frame temple portion 6 and the frame 1.
FIG. 6 schematically illustrates measurement of the distance. Here, a distance A from the operational manipulating position P to the carrier lens 5 and a horizontal distance B from the operational manipulating position P to the vertical line passing through the carrier lens 5 in the horizontal direction as being perpendicular thereto are actually measured using a scale in a state that the operator wears the frame 1 and takes a posture to perform surgery. Then, an angle a sandwiched thereby is obtained from the actually-measured distances A, B.
Meanwhile, when the operator takes a posture to perform surgery, the frame 1 is forwardly leant owing to forward-leaning of the head of the operator (FIG. 4). The forward-leaning angle s is about 25 degrees with surgery in a standing posture such as surgical operation and is about 20 degrees with surgery in a sitting posture such as dental operation. Accordingly, downward wearing angle r1, r2 being downward angles at which the right and left loupe units 2 are attached to the carrier lenses 5 are obtained from the angle a and the forward-leaning angle s being 25 degrees or 20 degrees corresponding to surgery at which the binocular loupe 10 to be manufactured is to be used.
(4) Manufacturing Binocular Loupe
After the inward wearing angles p, q and the downward wearing angle r1, r2 are determined, opening portions are formed at the right and left carrier lenses 5 respectively at attaching positions of the loupe units 2 which are determined from the right and left pupil positions obtained through measurement of the inter-pupil distance. Then, the loupe units 2 are fitted to the opening portions while keeping the inward wearing angles p, q and the downward wearing angles r1, r2, so that the binocular loupe 10 is manufactured.